Tamper-resistant hypodermic syringe

Abstract

Instances have been discovered in which a person has inserted the needle of a first hypodermic syringe through the soft rubber drive piston of a second hypodermic syringe to aspirate some of the narcotic fluid from the second syringe into the first syringe. To prevent this mode of pilfering, an impenetrable barrier is included in the second syringe to prevent the insertion of the needle of the first syringe. The impenetrable barrier may be a unitary portion of the screw that is normally included in the drive piston of the syringe, or the barrier may be a separate part molded into the drive piston.

What is claimed is: 
     
       1. A tamper-resistant hypodermic syringe comprising in combination: a tubular member having a proximal end which is unobstructed and having a distal end;   a drive piston positioned within said tubular member;   a non-retractable stopper having a longitudinal passage to permit the syringe to be used for aspiration, said non-retractable stopper located within said tubular member immediately adjacent the distal side of said drive piston, but not connected to said drive piston;   a barrier impenetrable by a hypodermic needle and affixed to said non-retractable piston whereby the attempted insertion of a hypodermic needle through said non-retractable piston from the proximal end of said tubular member will cause said non-retractable stopper to be pushed toward the distal end, thereby giving a visual indication that the syringe has been tampered with.   
     
     
       2. The improved drive piston of claim 1 wherein the difference between the diameter of the bore of the tubular member and the diameter of said head portion does not exceed the diameter of the smallest hypodermic needle that could be used to pilfer the contents of the hypodermic syringe.